Maintaining optimal reproductive health in the context of high HIV prevalence poses a serious dilemma for young rural Malawian women ages 15-20 who make behavioral choices regarding their sexuality and fertility that have health implications for them and their future children. Optimal reproductive health requires these preconceptual behaviors: safer sex (abstaining or using condoms) to prevent STIs, including HIV infection; treatment for STIs; maintaining good health habits such as diet, exercise and avoiding substance use; using an effective family planning method to prevent unintended pregnancy; and having an HIV test periodically and with the partner when conception is intended. However, no programs in Malawi offer a comprehensive, integrated approach to promoting optimal reproductive health. Also, we found no published programs that integrate issues of conceiving and HIV/STIs prevention. To fill this gap, we developed the Mzanga intervention, a community-based culturally grounded peer group intervention led by two trained community young women assisted by a local health worker. The Mzanga intervention integrates behavioral change models, contextual tailoring including developmental and gender issues, and WHO primary health care principles. We will test the efficacy of this intervention using a longitudinal, two-group comparison design with a delayed control group. Eighteen geographically separate rural communities will be stratified by size and distance from the main paved road and then randomly assigned to the intervention and delayed control conditions. After attrition, a final sample of 345 in the intervention and in the control groups will provide adequate power to detect medium effects. We hypothesize that at 9 and 15 months post-baseline (6 and 12 months post-intervention), compared to the control group, the intervention group will have more positive mediating and behavioral outcomes. Mediating outcome variables include knowledge, attitudes, perceived norms, self-efficacy, and intention for each of the behavioral outcomes. Behavioral outcomes are abstaining or consistently using condoms except when pregnancy is intended; seeking prompt treatment within two weeks at the health center for STI symptoms; maintaining a nutritious diet, exercising regularly, and avoiding substance use; using an effective family planning method except when pregnancy is intended, and having an HIV test periodically and with the partner when conception is intended. The intervention occurs across 9 waves, with 4 peer groups per wave. Following baseline assessment, the intervention group will receive the 8 session intervention. Outcomes will be evaluated at 9 and 15 months post-baseline. All evaluation will be conducted using an audio computer-assisted self-interview. The delayed control group will receive the intervention after the 15 month evaluation. Data will be analyzed using logistic and OLS regression. If this innovative intervention is effective, this research will make a major contribution toward promoting optimal reproductive health, including HIV prevention, for women and their babies in Malawi and throughout the African region.